When changing the assignment of a constructor call, the lifeline is not updated

[Matthias Schoettle]

When changing the assignment of a constructor call in a message view to a local property, the lifeline's represents remains unchanged, pointing to the wrong "representer".

Steps to reproduce:

• Create a new lifeline using a create message
• change the assignment by clicking on the plus button in the selector

When changing to an existing structural feature, it gets updated properly.

In the above case, the represents of the lifeline needs to be updated as well.

[Matthias Schoettle]

Resolves #252: Adds an additional command to be executed when a temporary assignment is created in case of a create message. The lifeline's represents needs to be set to the new assignment.

→ <<cset f700c9338a0f>>